I'm enjoying reading the replies on here, thank you for all your input, the idea of using a type of Mistel/Piggyback has appeal.
I was thinking how it could be achieved, A Spit on top of a Halifax sounds doable, but not a Tiffy as I think they would be too heavy.
I agree using Beaufighter's for escort in this timeframe wouldn't work as they could be a bit slow. I discounted the Mossie as in my narrative, they would be tasked with pathfinding and special ops, more than squandered on bomber escort.
I also think the Stirling will be an ideal assembly ship and restrict them for glider towing an paracute drops and leave the bombing to Halifax's (Daylight) and Lancasters (Night).
Single engined IFR? Both curious and dangerous as far as I can see, but can anyone answer that technical question, or restrict IFR to twin engined types?
As for one of my original questions, I was trawling the Wikipedia List of RAF Squadrons, I came up with this....
"No. 8 Group Bomber Command (Reformed as No. 8 (Bomber) Group on 1 September 1941, but disbanded on 28 January 1942.)
505 Squadron YF code (Not formed)
506 Squadron FS code (Not formed)
507 Squadron GX code (Not formed)
508 Squadron DY code (Not formed)
509 Squadron BQ code (Not formed)
513 Squadron CS code (Not formed)
(No. 513 Squadron RAF was a non-operational bomber squadron)
551 Squadron No code (Not allocated in real life)
552 Squadron No code (Not allocated in real life)
553 Squadron No code (Not allocated in real life)
554 Squadron No code (Not allocated in real life)
555 Squadron No code (Not allocated in real life)
556 Squadron No code (Not allocated in real life)
557 Squadron No code (Not allocated in real life)
558 Squadron No code (Not allocated in real life)
559 Squadron No code (Not allocated in real life)
560 Squadron No code (Not allocated in real life)
561 Squadron No code (Not allocated in real life)
562 Squadron No code (Not allocated in real life)
563 Squadron No code (Not allocated in real life)
564 Squadron No code (Not allocated in real life)
565 Squadron No code (Not allocated in real life)
566 Squadron No code (Not allocated in real life)
There were to have been Reserve squadrons using numbers 551–566 which would have been created by adding 500 to existing Operational Training Unit designations. In the event the plan was never put into effect, although there was some desultory use of some of the numbers by some of the OTUs for a short period. Despite their lack of formal activation, this block of numbers has never been re-allocated for use by other units."
So all I have to do is find homes for them!!